SPT-CL J2032-5627: a new Southern double relic cluster observed with ASKAP

TL;DR

This study reports the discovery of two new radio relics in galaxy cluster SPT-CL J2032-5627 using ASKAP and ATCA data, highlighting their properties and implications for future surveys.

Contribution

First detection of double radio relics in this cluster with detailed spectral analysis and discussion of their relation to cluster dynamics and survey capabilities.

Findings

Two new radio relics detected at 943 MHz with steep spectra.

Relics are below the current power-mass scaling relation.

ASKAP and ATCA have high sensitivity to low-surface brightness sources.

Abstract

We present a radio and X-ray analysis of the galaxy cluster SPT-CL J2032-5627. Investigation of public data from the Australian Square Kilometre Array Pathfinder (ASKAP) at 943 MHz shows two previously undetected radio relics at either side of the cluster. For both relic sources we utilise archival Australia Telescope Compact Array (ATCA) data at 5.5 GHz in conjunction with the new ASKAP data to determine that both have steep integrated radio spectra ($\alpha_\mathrm{SE} = -1.52 \pm 0.10$ and $\alpha_\mathrm{NW,full} = -1.18 \pm 0.10$ for the southeast and northwest relic sources, respectively). No shock is seen in XMM-Newton observations, however, the southeast relic is preceded by a cold front in the X-ray emitting intra-cluster medium. We suggest the lack of a detectable shock may be due to instrumental limitations, comparing the situation to the southeast relic in Abell 3667. We compare the relics to the population of double relic sources and find they are located below the current power-mass ($P$-$M$) scaling relation. We present an analysis of the low-surface brightness sensitivity of ASKAP and the ATCA, the excellent sensitivity of both allow the ability to find heretofore undetected diffuse sources, suggesting these low-power radio relics will become more prevalent in upcoming large-area radio surveys such as the Evolutionary Map of the Universe (EMU).